The invention relates to a vane pump for supplying fuel, the pump having associated means for regulating the pressure of fuel supplied by the vane pump. In particular, the invention relates to a vane pump for supplying fuel under pressure to a fuel injection pump.
In diesel engines, it is usual to use a transfer pump to supply fuel under pressure to a diesel fuel injection pump. The fuel pressure supplied to the fuel injection pump must be regulated and, in mechanically driven fuel injection pumps, this can be done by using a rotary vane pump as the transfer pump. An associated pressure regulator serves to control the fuel pressure supplied to the fuel injection pump from the outlet of the vane pump.
One type of conventional vane pump comprises a driven rotor arranged within a cylindrical member, commonly referred to as a liner, the liner having a non circular bore arranged eccentrically to the centre line of the driven rotor. The rotor rotates within the liner between two closure plates, an upper closure plate, commonly referred to as the distribution plate, and a lower plate. Apertures within the upper and lower closure plates define an inlet port and an outlet port within the vane pump housing.
Fuel is introduced into the vane pump through the inlet port and is carried around the pump by means of blades extending from the rotor and biased towards the inner surface of the liner. Fuel from the outlet port is supplied to a regulator arranged remotely from the vane pump which serves to regulate the fuel pressure supplied to a downstream fuel injection pump by recirculating some of the fuel from the vane pump outlet back into the vane pump inlet.
The regulator usually consists of a cylindrical body housing a spring biased piston. It is necessary to form several drillings within the regulator body to accommodate the piston and to provide the channels required to effect the regulatory function of the device. Where the regulator body is within a housing common to the vane pump and/or the fuel injector pump itself, it is also necessary to form additional drillings in the housing. The construction of a conventional vane pump is therefore complex and manufacture is difficult and expensive. In addition, the device can be bulky as the regulator is arranged remotely from the rotary part of the vane pump.
It is an object of the present invention to provide a vane pump of reduced complexity which alleviates the manufacturability problems of the prior art. It is a further object of the present invention to provide a vane pump which has a reduced size.
According to the present invention, there is provided a vane pump, having an inlet for receiving fuel and an outlet from which fuel is supplied, comprising;
a generally cylindrical member;
a driven rotor arranged within the cylindrical member; and
a closure member, the cylindrical member and the closure member co-operating to define a recirculation passage interconnecting said outlet and said inlet, the output pressure of fuel discharged from the pump being regulated by resiliently biased valve means controlling the flow of fuel through said recirculation passage.
In one embodiment of the invention, the closure member may form part of the pump housing.
The cylindrical member may have a first channel defined therein co-operating with a second channel defined in the closure member, the first and second channels defining the recirculation passage.
Alternatively, the recirculation passage may be defined by a channel formed in the cylindrical member, the closure member cooperating with the cylindrical member to define an inner surface of the recirculation passage.
As the only machinings required for the regulatory function are the first and second channels within the closure member and the cylindrical member, the vane pump of the invention is considerably less complex than a conventional vane pump, therefore providing advantages in terms of manufacturing difficulty and cost. Additionally, as the means for regulating the fuel pressure are arranged within the cylindrical member and closure member assembly, the vane pump is of reduced size.
The valve means may be in the form of a compression spring housed within the recirculation passage, the spring biasing an abutment member into communication with an opening of the recirculation passage to control the flow of fuel supplied to the recirculation passage. Conveniently, the abutment member may be a ball.
In an alternative embodiment, the biasing means may be a leaf spring biased into communication with an opening of the recirculation passage to control the flow of fuel supplied to the recirculation passage. In a further alternative embodiment, the vane pump may comprise a third passage defined within the cylindrical member and communicating with the recirculation passage, the supply of fuel to the third passage being regulated by means of a piston member operating under a spring biasing force. This embodiment is particularly useful for supplying fuel to a mechanically driven fuel injection pump, requiring a speed dependent fuel pressure.